With the development of communication technologies, computer networks enter all aspects of human lives. The second generation Internet based on the Internet Protocol Version 4 (IPv4) becomes a bottleneck of launching network services as IPv4 address resources are about to be exhausted soon. Thus, the Internet Engineering Task Force (IETF) provides a series of technology means for effectively slowing down IPv4 address exhaustion, which includes: Private IP Address Space; Dynamic IP Address Allocation; Variable Length Subnet Mask; Classless Inter-Domain Routing (CIDR); and Network Address Translation/Network Address Port Translation (NAT/NAPT). With the deployment of the 3G, Next Generation Network (NGN) and IP multimedia systems and the development trend of the all IP, a great amount of IP addresses need to be consumed, which forces to expedite commercial use of the Internet Protocol Version 6 (IPv6). However, transition from the IPv4 to the IPv6 involves enormous work of upgrading and modifying systems of hosts and routers, which is impossible to be accomplished in a short time, the IPv4 and the IPv6 will coexist in a long term. Hence, how to fully utilize the existing IPv4 network to gradually increase deployment of the IPv6 network and to realize communication is an industry focus.